| 引用本文: | 马秋晨,赵宪明,侯泽然.冷却工艺对20CrMnTi组织转变与硬度的影响[J].材料科学与工艺,2019,27(5):7-13.DOI:10.11951/j.issn.1005-0299.20180083. |
| MA Qiuchen,ZHAO Xianming,HOU Zeran.Effect of cooling processes on microstructure transformation and hardness of 20CrMnTi[J].Materials Science and Technology,2019,27(5):7-13.DOI:10.11951/j.issn.1005-0299.20180083. |
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| 摘要: |
| 探索合理的轧后冷却工艺制度对降低热轧齿轮钢棒材冷后硬度具有重要的指导意义.本文通过热模拟试验机进行冷却工艺试验，研究了单道次变形后不同冷却速度和不同终冷温度对齿轮钢20CrMnTi组织转变与硬度的影响.研究结果表明：在快冷速(10, 50 ℃/s)条件下，再结晶晶粒长大受到抑制，奥氏体晶粒细化，晶界面积增大，铁素体形核质点增多; 当终冷温度升高时，高温区铁素体相变时间增加，冷后组织中铁素体体积分数增大，硬度值降低.在终冷温度850 ℃时铁素体体积分数达到最大值58%，硬度值相应降低为264HV.在慢冷速(0.1 ℃/s)条件下，再结晶晶粒长大明显，铁素体形核质点减少，但随着终冷温度降低，两相区中C元素扩散时间延长，铁素体形核长大时间增加，冷后组织中铁素体体积分数增大，硬度值降低.在终冷温度760 ℃时铁素体体积分数达到最大值48%，相应硬度降低为最小值240HV.在1 ℃/s条件下，终冷温度对铁素体体积分数及硬度影响较小，铁素体体积分数和硬度分别在34%±4%和(282±5)HV范围内波动. |
| 关键词: 冷却工艺 20CrMnTi 奥氏体晶粒 动态再结晶 铁素体体积分数 |
| DOI：10.11951/j.issn.1005-0299.20180083 |
| 分类号:TG335.6+2 |
| 文献标识码:A |
| 基金项目:国家重点研发项目(2017YFB0304201). |
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| Effect of cooling processes on microstructure transformation and hardness of 20CrMnTi |
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MA Qiuchen,ZHAO Xianming,HOU Zeran
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(State Key Lab of Technology & Automation(Northeastern University), Shenyang 110004,China)
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| Abstract: |
| Developing an appropriate cooling process after rolling has important guiding significance for reducing the hardness of hot-rolled gear steel bars. In this paper, the effect of different cooling rates and final cooling temperatures after single-pass deformation on microstructure transformation and hardness of gear steel 20CrMnTi was investigated using a thermal simulator. The results indicated that grain boundary areas and ferrite nucleation sites increased due to inhibited growth of recrystallized grain and refined austenitic grain in rapid cooling conditions(10, 50 ℃/s).Moreover, with final cooling temperature increased, prolonged transformation time of ferrite in higher temperature region led to increased volume fraction of ferrite and decreased hardness. The maximum volume fraction of ferrite reached 58% and hardness correspondingly decreased to 264HV at final cooling temperature of 850 ℃. At slow cooling rates (0.1 ℃/s), recrystallized grains significantly grew, leading to decreased nucleation sites of ferrite. However, as final cooling temperature decreased, volume fraction of ferrite increased and hardness correspondingly decreased as a result of time increase for carbon diffusion in two-phase region and ferrite nucleation and growth. The maximum volume fraction of ferrite reached 48% and hardness decreased correspondingly to 240HV at final cooling temperature of 760 ℃. Different final cooling temperatures had less effects on volume fraction of ferrite and hardness at a cooling rate of 1 ℃/s. Thus, volume fraction and hardness of ferrite fluctuated within the range of 34%±4% and (282±5)HV. |
| Key words: cooling processes 20CrMnTi austenitic grain dynamic recrystallization volume fraction of ferrite |
